1. Field of the Invention
An aspect of this disclosure relates to an etching method.
2. Description of the Related Art
There exists a method where holes with a high aspect ratio are etched in a silicon dioxide film under a low-temperature environment (see, for example, Japanese Laid-Open Patent Publication No. 07-22393). For example, in producing a three-dimensional multilayer semiconductor memory, this method makes it possible to etch holes or grooves with a high aspect ratio in a multi-layer film of silicon dioxide and silicon nitride and in a single-layer film of silicon dioxide.    [Patent document 1] Japanese Laid-Open Patent Publication No. 07-22393    [Patent document 2] Japanese Laid-Open Patent Publication No. 62-50978    [Patent document 3] Japanese Laid-Open Patent Publication No. 07-22149    [Patent document 4] Japanese Patent No. 2956524
With the above method, however, when the multi-layer film and the single-layer film are processed concurrently, the processing time becomes long and the productivity is reduced due to the difference in the etching rate between the multi-layer film and the single-layer film.
Also, in plasma etching, it is important to prevent the increase in the temperature of a substrate due to heat input from plasma and to evenly etch a multi-layer film of silicon dioxide and silicon nitride and a single-layer film of silicon dioxide.